Oh yes, I remember the day when my seemingly cute harmless kitten finally got big enough to knock my small aquariums off the mantle and kill my fish. I was horrified. :( Now I am thinking of getting some of that industrial velcro sticky strips from Home Depot to anchor my 3 gallon critter keeper just in case...

I'm not a cat person really, Im a ferret person. I currently have three. I have only had the fish for about four months but I can still remember the first week I got them. I was setting up my tanks and Stumpy(My three footed half tailed sable male) would sit on my foot and watch the first time I turned my back on him he got on the table I caught him just as he opened the lid. Clever boy.
He also insisted to steal the little containers of fish food I found him sleeping curled around blood worms and betta-min. Tricky devil.

Also my ferret rose can open cupboard doors as well, she choose to steal the gallon of linaton that is hidden their it is quite funny to watch her attempt to drag of a gallon of liquid. Its crazy seeing some of the things they steal when you arent looking.

My cat, fortunately, lives outside (and in our garage when it gets cold, don't worry). But every time she does manage to get in, she heads straight for our 55 gallon tank and just stares at the fish. My dad made a built-in shelf to house the aquarium and make storage above it, so there's enough room to get the lid off, but not enough for my cat to get on top of it. I know she wants too, though. I would not trust her around my betta.

My best friend's ferret used to steal everything! I mean everything. He had this huge green glass jar in her room and he'd stash everything in there. We had to check it daily. I always wanted one cause their such lil thieves. The image of a ferret wrapped around a thing of fish food cracked me up. Lol!

It wasnt just one it was three different kinds he also had a menagrie of paper rolled into balls, lids from different things, my shoe(only one of course he stashed the other some where else) and my spare car key. *sigh*